Hydrostatic power steering system with curved valve return springs

摘要

A flow control valve for a power steering system of the kind having a metering pump is provided with a leaf spring device stressed upon rotation of a hand steering wheel to operate a valve sleeve and the metering pump. The spring device provides a force for returning the valve sleeve to neutral position after a steering operation and comprises curved or arched springs between pressure plates. The convex sides are back-to-back between pressure plates and have curved ends supported on and shaped to slide on the pressure plates with minimum friction as the springs are compressed. The pressure plates are uniquely shaped in the central areas for providing flexibility to compensate for manufacturing inaccuracies. The spring device is assembled in a carrier with the pressure plates under initial compression and an actuating sleeve within the valve sleeve is rotated by a manual force on a steering wheel to stress the springs and to rotate the metering pump and, via a coarse threaded connection, shift the valve sleeve axially for flow control to a servomotor. The springs are elongated in the axial direction of the valve sleeve and operated by stressing their margins between the actuating sleeve and a spring assembly carrier, the arrangement being such that no direct contact between the springs or pressure plates acts against the valve sleeve. However, the initial compression of the springs ensures a force for maintaining the valve sleeve in neutral position.